Many heating means are used for ink or toner fixation or for photosensitization in a copying machine and the like. For example, many heating means are used in a long substrate such as a toner fuser of a copying machine or a drying roll of an automatic developing machine. Structures such as a heating plate or a heating roll are adopted as such heating means. Further, such heating structures are usually in the form of a laminated structure.
Since heating structures such as a heating plate or a heating roll are required to have not only a high heat resistance as heating elements but also a dimensional accuracy and a surface smoothness, the conventionally used ones are in the form of a structure comprising a ceramic or like base having a high heat resistance and a good dimensional accuracy and a metallic resistor laminated on the surface of the base. However, a ceramic base is very expensive because it is produced by cutting a sintered ceramic, and involves a demerit of difficulty in handling because it is liable to crack.
Moreover, such a structure involves not only the problem of necessity of a large electric power because it has a comparatively high thermal conductivity and is hence liable to dissipate heat, but also the problem of long heating time (build-up time) required till it reaches a predetermined temperature because it has a comparatively large heat capacity.
An object of the present invention is to solve the foregoing problems of the prior art to thereby provide an inexpensive laminated heating structure excellent in heat resistance, dimensional accuracy and mechanical strength, reduced in electric power consumption, and shortened in build-up time.